The early development of the cellular components of the lympho-myeloid complex in the leopard frog, Rana pipiens is being investigated. The basic experimental approach is the reciprocal transplantation of presumptive hematopoietic anlagen between diploid (2N) and triploid (3N) from embryos. The cellular components of hematopoietic organs in experimental larvae are subsequently analyzed using microdensitometric methodologies in order to distinguish the embryo origin of the particular components. The leopard for model also provides an opportunity for investigating correlations between early embryonic events and functional development of competent hematopoietic cells within a single individual.